The valence electron photoemission spectrum of semiconductors: ab initio description of multiple satellites

TL;DR

This paper develops an advanced theoretical approach to accurately describe the complex valence band photoemission spectra of semiconductors, including multiple satellites, surpassing the limitations of the GW approximation.

Contribution

It introduces a new approximation based on a functional differential equation for the Green's function, achieving excellent agreement with experimental spectra and suggesting a dynamical vertex correction beyond GW.

Findings

Accurately reproduces experimental spectra including multiple satellites

Identifies limitations of the GW approximation in describing satellite structures

Proposes a new theoretical framework for improved spectral calculations

Abstract

The experimental valence band photoemission spectrum of semiconductors exhibits multiple satellites that cannot be described by the GW approximation for the self-energy in the framework of many-body perturbation theory. Taking silicon as a prototypical example, we compare experimental high energy photoemission spectra with GW calculations and analyze the origin of the GW failure. We then propose an approximation to the functional differential equation that determines the exact one-body Green's function, whose solution has an exponential form. This yields a calculated spectrum, including cross sections, secondary electrons, and an estimate for extrinsic and interference effects, in excellent agreement with experiment. Our result can be recast as a dynamical vertex correction beyond GW, giving hints for further developments.